Shakirov, Z. G., and A. R. Bagautdinov. “To The Question Of Urbanization In The Territory Of The Pre-Mongol Volga Bulgaria”. Revista Publicando, vol. 4, no. 13 (3), Dec. 2017, pp. 992-1000, https://revistapublicando.org/revista/index.php/crv/article/view/1022.